This invention relates to an electronic component, especially to a structure of packaging an electronic element and a method of fabricating the same.
For some electronic elements, for example, surface acoustic wave (SAW) filters, it is necessary to package the filters in outer cases with some space between the filters and the inside of the case. Conventionally, a surface acoustic wave filter has been packaged in a case consisting of upper and lower cases welded together, keeping a small space upon or over the filter. The container for the filter was made from upper and lower cases of metal, for example kovar (well known alloy of Fe, Ni and Co) plated with gold, nickel, or the like. The cases were provided with brims. A pair of electric welding electrodes pressed the brims of the cases from both sides to flow a strong current to melt and fix them together. The heat from the welding caused small parts of the metal to be evaporated, and cover the surface of the aluminum of the SAW filter. Further, in the prior art, the substrate supporting the SAW filter was often fixed in the case by a silicon resin. This silicon resin was heated to fix the substrate in place. As a result, some of the resin evaporated and was deposited on the aluminum surface of the SAW element.
The deposits of metal and resin on the SAW filter often had adverse effects on the operating characteristics of the filter. For example, the frequency of the SAW filter was caused to shift adversely. The present invention prevents the adverse effects of these deposits on the elements housed in the package described in further detail hereinafter.